| 1001 | Osage Operating Company LLC | Seattle, WA 98133 | Oil Operator | May 2006 |
| 1002 | Osage Partners LLC | | Oil & Gas Operator | Aug 2025 |
| 1003 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Jun 2025 |
| 1004 | Ott Inc | Casper, WY 82602 | Oil Operator | Jul 2025 |
| 1005 | Overland Resources LLC | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Jul 2019 |
| 1006 | Ovintiv USA Inc. | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 1007 | Oxbow Properties Inc | Centennial, CO 80122-1422 | Oil & Gas Operator | Jan 2025 |
| 1008 | Oxford Exploration Company | Denver, CO 80237 | Oil & Gas Operator | Aug 1995 |
| 1009 | Oxtex Inc | | Oil & Gas Operator | Oct 1989 |
| 1010 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 1011 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 1012 | Qep Energy Company | Midland, TX 79701 | Oil & Gas Operator | Jun 2025 |
| 1013 | Qualmay Development LLC | Cody, WY 82414 | Oil & Gas Operator | Jun 2023 |
| 1014 | Quest Operating LLC | Sheridan, WY 82801 | Gas Operator | Sep 2008 |
| 1015 | Quicksilver Resources Inc | Fort Worth, TX 76102 | Oil & Gas Operator | Mar 2018 |
| 1016 | Quinoco Petroleum Inc | | Oil & Gas Operator | Dec 1990 |
| 1017 | Quintana Petroleum Corporation | Denver, CO 80265 | Oil & Gas Operator | Mar 1998 |
| 1018 | Rael Resources LLC | Cowley, WY 82420 | Oil Operator | Aug 2025 |
| 1019 | Rainbow Oil Company | | Oil & Gas Operator | Aug 1999 |
| 1020 | Rainbow Resources, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Aug 2007 |
| 1021 | Ramco Oil & Gas Inc | Midland, TX 79701 | Oil & Gas Operator | Nov 2006 |
| 1022 | Ranch Oil Company | West Linn, OR 97068 | Oil & Gas Operator | Aug 2025 |
| 1023 | Ranck Oil Company | Cut Bank, MT 59427 | Oil & Gas Operator | Jun 2025 |
| 1024 | Ranger Holdings Co | | Oil & Gas Operator | Jul 1993 |
| 1025 | Rangeview Resources Operating Co | | Oil & Gas Operator | Jul 2025 |
| 1026 | Rathbun Roger | | Oil & Gas Operator | Dec 1993 |
| 1027 | Rathpro Inc | Douglas, WY 82633 | Oil & Gas Operator | Feb 1994 |
| 1028 | RB Operating Company | Shawnee, OK 74802-1488 | Oil & Gas Operator | Apr 2015 |
| 1029 | RDG Oil & Gas LLC | Post Falls, ID 82854 | Oil & Gas Operator | Mar 2017 |
| 1030 | Reading & Bates Petroleum | | Oil & Gas Operator | Apr 1989 |
| 1031 | Red River Oil & Gas LLC | Cherry Hills, CO 80110 | Oil & Gas Operator | Feb 2025 |
| 1032 | Red Tiger Oil & Gas LLC | Gillette, WY 82718 | Oil & Gas Operator | Jul 2025 |
| 1033 | Redbud E & P, Inc. | Giddings, TX 78942 | Oil & Gas Operator | Oct 2025 |
| 1034 | Redstone Gas Partners LLC | Denver, CO 80202 | Gas Operator | Mar 2001 |
| 1035 | Redstone Resources Inc | Newcastle, WY 82701 | Gas Operator | Dec 2010 |
| 1036 | Reef Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Feb 2007 |
| 1037 | Reliance Resources Inc | Houston, TX 77007 | Gas Operator | Jun 2012 |
| 1038 | Remuda Energy Development LLC | Billings, MT 59104 | Oil & Gas Operator | Aug 2025 |
| 1039 | Renor Exploration | Englewood, CO 80111 | Oil Operator | Feb 2001 |
| 1040 | Renos Land & Minerals Company | Casper, WY 82601 | Oil & Gas Operator | Oct 2021 |
| 1041 | Reserve Oil & Gas Company | | Oil & Gas Operator | Jul 1981 |
| 1042 | Reserve Operating Corp. | Houston, TX 77040 | Oil & Gas Operator | Oct 2025 |
| 1043 | Resolute Wyoming Inc | Denver, CO 80203 | Oil & Gas Operator | May 2018 |
| 1044 | Resource Enterprises Inc | Salt Lake City, UT 84108 | Gas Operator | Dec 1990 |
| 1045 | Resources Investment Corp | Denver, CO 80202 | Oil & Gas Operator | Sep 2018 |
| 1046 | Reunion Energy Company | Houston, TX 77056 | Oil & Gas Operator | May 1996 |
| 1047 | Rex Energy Rockies LLC | State College, PA 16801 | Oil & Gas Operator | May 2013 |
| 1048 | Riata Energy Inc | Oklahoma City, OK 73101 | Oil & Gas Operator | Apr 2008 |
| 1049 | Richardson Oil Company | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2003 |
| 1050 | Richardson Operating Company | Denver, CO 80237 | Oil & Gas Operator | Jul 2025 |
| 1051 | Ridge Energy Partners LLC | Casper, WY 82601 | Oil Operator | Dec 2018 |
| 1052 | Ridgeland Wyoming Inc | | Oil Operator | Dec 2014 |
| 1053 | Rim Operating, Inc. | Englewood, CO 80112 | Oil & Gas Operator | Oct 2025 |
| 1054 | Rio Blanco Energy, Inc. | Littleton, CO 80121 | Oil & Gas Operator | Oct 2002 |
| 1055 | River City Resources Inc | Tulsa, OK 74119 | Oil & Gas Operator | Nov 1997 |
| 1056 | River Gas Corporation | Tuscaloosa, AL 35406-2233 | Gas Operator | Dec 2000 |
| 1057 | Rki Exploration & Production LLC | Tulsa, OK 74172 | Oil & Gas Operator | Oct 2025 |
| 1058 | Rme Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Nov 2016 |
| 1059 | Robert Hawkins Inc | Kevin, MT 59454 | Oil & Gas Operator | Jul 2025 |
| 1060 | Rochelle Oil & Gas | Gillette, WY 82717 | Oil & Gas Operator | Mar 2024 |
| 1061 | Rock Creek Resources LLC | Englewood, CO 80112 | Oil & Gas Operator | Dec 2021 |
| 1062 | Rock Oil Corporation | Lawrence, KS 66046 | Oil Operator | Oct 2004 |
| 1063 | Rock River Operating Inc | Laramie, WY 82070 | Oil & Gas Operator | Jun 2025 |
| 1064 | Rockies Resources Holdings LLC | Lakewood, CO 80228 | Oil & Gas Operator | Jul 2025 |
| 1065 | Rocky Mountain Gas Inc | Sheridan, WY 82801 | Gas Operator | Nov 2009 |
| 1066 | Rocky Mountain Operating Co Inc | Littleton, CO 80121 | Oil & Gas Operator | Dec 2011 |
| 1067 | Roemer Oil Company | Denver, CO 80202 | Oil & Gas Operator | Nov 1998 |
| 1068 | Roff Operating Company LLC | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 1069 | Ronadero Company Inc | Roswell, NM BAD ADDR | Oil & Gas Operator | Dec 1996 |
| 1070 | Rosa Petroleum | Evansville, WY 82636 | Oil Operator | Dec 1995 |
| 1071 | Royal Oil LLC | Flower Mound, TX 75028 | Oil Operator | Dec 2015 |
| 1072 | Royal Resources Exploration | | Oil & Gas Operator | Mar 1984 |
| 1073 | Ruby Drilling Company Inc | Gillette, WY 82718 | Oil Operator | Oct 2007 |
| 1074 | S & J Operating Company | Wichita Falls, TX 76301 | Oil & Gas Operator | Mar 2015 |
| 1075 | Saba Energy Of Texas Inc | Houston, TX 77042 | Oil & Gas Operator | Jul 2007 |
| 1076 | Sabine Corporation | Oklahoma City, OK 73116 | Oil & Gas Operator | Jul 1996 |
| 1077 | Sabine Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 1078 | Saga Petroleum LLC Of Colorado | Norman, OK 73072 | Oil & Gas Operator | Oct 2025 |
| 1079 | Sage Butte PRB Operating, LLC | Denver, CO 80202 | Oil & Gas Operator | Aug 2025 |
| 1080 | Sage Petroleum LLC | Casper, WY 82601 | Oil Operator | Jun 2008 |
| 1081 | Salt Creek Operating LLC | FT Morgan, CO 80701 | Oil & Gas Operator | Mar 2020 |
| 1082 | Salt Creek West Partners | | Oil Operator | Jul 1995 |
| 1083 | Samedan Oil Corporation | Houston, TX 77067 | Oil & Gas Operator | Dec 2019 |
| 1084 | Samson Exploration LLC | Tulsa, OK 74101 | Oil & Gas Operator | Aug 2025 |
| 1085 | Samson Oil & Gas USA Inc | Denver, CO 80202 | Oil & Gas Operator | Aug 2025 |
| 1086 | Samson Resources Company LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2021 |
| 1087 | San Marco Petroleum Inc | Denver, CO 80293 | Oil & Gas Operator | Jun 2025 |
| 1088 | Sanchez-O'Brien | | Oil & Gas Operator | Dec 1984 |
| 1089 | Sands Oil Company Inc | Billings, MT 59103 | Oil & Gas Operator | Jul 2025 |
| 1090 | Sands-American Corp | | Oil & Gas Operator | Jan 1990 |
| 1091 | Santa Rosa Petroleum LLC | Recluse, WY 82725 | Oil & Gas Operator | Aug 2025 |
| 1092 | Sauer Bill Oil & Gas Company LLC | Casper, WY 82604 | Oil & Gas Operator | Jun 1999 |
| 1093 | Saxon Oil Company | Dallas, TX 75204 | Oil & Gas Operator | Oct 2009 |
| 1094 | Sayers Operating Company | Midland, TX 79705 | Oil & Gas Operator | Feb 2005 |
| 1095 | Scana Petroleum Resources Inc | Houston, TX 77002 | Oil & Gas Operator | Jun 2013 |
| 1096 | Scarlett Energy Enterprises LLC | Watchung, NJ 07069 | Oil & Gas Operator | Oct 2014 |
| 1097 | Sceptre Resources Inc | | Oil & Gas Operator | Dec 2007 |
| 1098 | Schiff & Jackson Oil Producers | Dallas, TX 75206 | Oil & Gas Operator | Jun 2025 |
| 1099 | Schlaikjer A L | | Oil Operator | Feb 1997 |
| 1100 | Schmid Properties Inc | Hico, TX 76457 | Oil & Gas Operator | Oct 2025 |